The long-term goal of the proposed studies is to understand the molecular mechanisms that determine longevity. Animal species differ enormously in their aging rates. Therefore, comparative approach is a powerful tool to obtain new insights into the mechanisms of aging. The nutrient sensing IGF-1 and mTOR pathways play major roles in aging. This RFA calls for the analysis of the role these conserved nutrient sensing pathways play in regulating lifespan in a wider range of vertebrate species. In this application we propose to identify differences in IGF-1 and mTOR pathways between short-and long-lived species of rodents. Rodents are an ideal species group for this study as it includes phylogenetically related species with diverse lifespans, in which slow aging has evolved independently several times. We are uniquely equipped to carry out the proposed research. Our laboratory has assembled a collection of primary cells and tissues from 18 rodent species, and performed preliminary analysis of IGF-1 signaling in these species. Our preliminary data show that IGF-1R levels negatively correlate with lifespan in the brain tissue of long-lived rodents, bu not in the peripheral tissues. The proposed study will perform systematic analysis of IGF-1 and mTOR signaling in a panel of 18 rodent species with diverse lifespans. We will address the following questions: Does IGF-1 and mTOR signaling correlate with longevity at the interspecies level? Has natural selection used downregulating these signaling pathways as a way to evolve longer lifespan, or are the mechanisms that can extend lifespan of individual species fundamentally different from the mechanisms used on evolutionary scale? What tissues are important? In this application we will employ the collection of primary rodent cells and tissues to (1) Perform comparative analysis of the IGF-1 pathway; and (2) Perform comparative analysis of the mTOR pathway. We will examine the differences in the basal levels of activity of these pathways, and the strength and kinetics of the response upon stimulation. We will then statistically evaluate the relationship between the IFG-1 and mTOR pathway activity and lifespan. The data will be corrected for phylogenetic nonindependence, and controlled for confounding variables such as body size. In the next three years, when the complete transcriptome sequence of the species in our collection will become available, through the ongoing funded collaboration, we will use the information from the current pilot study to perform proteomics analysis of these pathways by mass spectrometry. The proposed study will determine whether there is a correlation between the activity of IGF-1 and mTOR pathways and longevity across species and identify the tissues in which these pathways are down-regulated in long-lived species. This work is essential for understanding evolution of longevity. Furthermore, if tissues critical for down-regulation of the IGF-1 and mTOR pathways are identified they will be used as targets for intervention in humans.